589
FXUS65 KGJT 210003
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
603 PM MDT Thu Aug 20 2026

.KEY MESSAGES...

- Isolated showers and thunderstorms expected over the high
  terrain today and Friday. Main concerns will be gusty outflow
  winds and lightning.

- Triple-digit temperatures expected today and Friday in lower
  valleys.

- Precipitation potential increases this weekend with more
  widespread coverage of showers and thunderstorms. Flash
  flooding will be possible, especially Saturday.

&&

.DISCUSSION...
Issued at 1216 PM MDT Thu Aug 20 2026

Some morning convection occurred as a weak shortwave moved
through the area, exiting by mid morning. High pressure remains
in place across the area with residual moisture trapped
underneath the high allowing for isolated to scattered afternoon
convection over the high terrain. A vort max does look to track
across the north this evening into the overnight which could
result in some lingering activity, but overall should be a hot
and dry day otherwise. Friday begins a transition day with a low
pressure trough approaching the Pacific Northwest coast.
However, high pressure still remains anchored over the Four
Corners region, providing another day of scattered showers and
thunderstorms mainly over the high terrain. The main concerns
with any storm activity remain gusty outflow winds to 35 mph and
lightning with some localized wetting rain in the stronger
convection. While hydro concerns will be minimal through Friday
due to the drier low levels, stronger convection could still
result in an isolated flash flood risk over burn scar areas. The
main point of interest as we close out the work week will be
the abnormally warm temperatures underneath this high pressure,
with triple digits possible in many valley locations Thursday
and Friday, particularly the lower desert valleys of eastern
Utah and west-central Colorado. Because of the lingering
moisture in the Intermountain West, cloud cover will play a role
in just how hot these temperatures will be allowed to get, but
regardless, look for highs to remain about 10 degrees above
normal until we hit the weekend.

WET WEATHER RETURNS THIS WEEKEND:

Saturday begins the ramp up in wet weather returning to the
region as the low pressure trough pushes inland across the
Pacific Northwest and nudges the high pressure ridge eastward,
putting us in a more favorable trajectory for monsoonal moisture
to surge back northward in southerly flow. While the strongest
portion of this moisture plume will push across the Great Basin
to our west with PWAT anomalies increasing towards 200 percent
of normal, PWAT will increase towards an inch or greater across
our CWA on Saturday, which is still a good jump from where it
stands currently. Dew points also rise well into the 50s for
much of the area. Hydro impacts become more probable during this
period as a robust shortwave moves through the southerly flow
late Saturday afternoon into the evening across eastern Utah and
moves through northwest Colorado over the top of the ridge by
Saturday evening and overnight. This added forcing combined with
the increase in moisture could result in more widespread storm
activity late in the day on Saturday and potentially continuing
overnight, including a better chance of wetting rain in the
lower elevations as well. The aforementioned Pacific Northwest
trough looks to move across the northern Rockies Sunday, so with
moisture already in place, this will result in more scattered
thunderstorm development as the flow becomes more westerly. Due
to the projected placement of this shot of moisture, there`s
still wiggle room for models to nudge it further into our CWA,
so don`t count out a more widespread event. As guidance stands
now though, the flash flood risk appears more moderate with
highest potential over the burn scar areas. Hi-res models will
reveal much more insight into this system, so stay tuned as we
begin to receive this model guidance over the coming days.

It does appear like drier air tries to work back in for early
to mid next week as the high pressure shifts back a bit westward
and builds overhead. However, lingering moisture will still
result in daily afternoon thunderstorms favoring the high
terrain but the coverage does not appear as widespread as this
weekend with the deeper moisture and more robust forcing in
place. Temperatures are expected to cool a bit closer to normal
this weekend into early next week with the increase in clouds
and precipitation.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 558 PM MDT Thu Aug 20 2026

Showers and thunderstorms will taper off this evening, with VFR
conditions continuing through the overnight hours. Breakpoint
conditions are not expected. Gusty outflows and small hail
remain a concern near any thunderstorms. Winds remain light
through tomorrow morning, with showers and thunderstorms
becoming more widespread Friday afternoon.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

DISCUSSION...MDA/TGJT
AVIATION...TGJT